/** To be provided by the particular implementation. **/
extern int fetch(unsigned char *sha1);
+extern int fetch_ref(char *ref, unsigned char *sha1);
+
+/** If set, the ref filename to write the target value to. **/
+extern const char *write_ref;
+
+/** If set, the hash that the current value of write_ref must be. **/
+extern const unsigned char *current_ref;
+
/** Set to fetch the target tree. */
extern int get_tree;